Automatized complex for fatigue life testing Neimark, A.S., Ryzhev, E.E. and Gorelov, V.N. Industrial Laboratory (Russia) (Nov. 1993) 59 (5), 509–511

1995 ◽  
Vol 17 (1) ◽  
pp. 74
Keyword(s):  
Fatigue Life ◽  
Life Testing ◽  
Industrial Laboratory

Fatigue Margins Established by Unit and Spacecraft Protoqualification Tests

2010 ◽  
Vol 53 (2) ◽  
pp. 24-34
Author(s):  
Enold Pierre-Louis
Keyword(s):  
Fatigue Life ◽  
Random Vibration ◽  
Low Cycle Fatigue ◽  
Test Procedure ◽  
Cyclic Fatigue ◽  
Acceptance Test ◽  
Cycle Fatigue ◽  
Life Testing ◽  
Thermal Range ◽  
Life Factor

Protoqualification (PQ) testing, typically performed on the first assembled electronic units and spacecraft, establish random vibration and thermal cycling fatigue margins for subsequent builds that are only subjected to the acceptance test program (ATP). Considering the fatigue damage induced by both unit- and spacecraft-level testing, fatigue margins are calculated for equipment exposed to ATP-level testing. Probabilistic analyses are also performed to determine the relationship between the fatigue margin and the demonstrated reliability for the unit to survive the mission. Parameters such as the number of retests and the material dependent fatigue acceleration exponent are considered. Using MIL-STD-1540E,1 PQ random vibration test guidelines of three decibels (+3 dB) above the acceptance input level for 2-minute-per-axis duration, the assessment shows that the test establishes ample fatigue margin for units subjected to the less stringent ATP. The probabilistic analysis shows that the established reliability to survive the launch environment without a fatigue induced failure is adequate. It is further shown that the desired high-cycle fatigue life factor of greater than four is maintained even after one unit retest is performed. However, since this conclusion is general in nature, it is important that for future spacecraft, assessments be performed for both PQ and ATP hardware, taking into account each specific design and application to verify that adequate fatigue margin exists to survive launch. Because mission thermal cyclic environments vary greatly with regard to the number of cycles and the extent of the thermal range for each cycle, MIL-STD-1540E PQ guidelines for unit-level testing were designed to verify the design and workmanship and not intended to demonstrate fatigue margin for specific missions. Rather, MIL-STD-1540E specifies that thermal cyclic fatigue margin for the combination of pre-launch and orbital environments should be demonstrated with life testing. Accordingly, the analysis shows that PQ testing only demonstrates the desired low-cycle fatigue life factor of 2 for subsequent units which are subjected to a single ATP. The fatigue life factor falls below 2 when retests and/or mission thermal cyclic environments are considered. Because acceptable fatigue margin is not established with the standard PQ thermal cycle test procedure, it is essential that other means be taken to ensure that adequate fatigue margin exists. This paper provides guidelines for using analyses and offline life testing to assess the fatigue life of critical units and their internal components for pre-launch and orbital thermal cyclic environments.

scholarly journals A Study on Failure Analysis and High Performance of Hydraulic Servo Actuator

2020 ◽  
Vol 10 (21) ◽  
pp. 7451
Author(s):  
Yong-bum Lee ◽  
Jong-won Park ◽  
Gi-chun Lee
Keyword(s):  
Fatigue Life ◽  
Accelerated Life Testing ◽  
Test Equipment ◽  
Life Testing ◽  
Life Test ◽  
Accelerated Life ◽  
Servo Actuator ◽  
Hydraulic Servo ◽  
Automotive Parts ◽  
Fatigue Life Test

Hydraulic servo actuator is used as the core actuator in tensile compression fatigue life test equipment as it operates the micro displacement very precisely at a high frequency and can be used continuously for a long period of time. Recently, the life expectancy of automobiles has been extended, the load conditions of accelerated life testing on auto parts have been increased, and the life test time and number of tests have increased significantly in order to secure the reliability of the guaranteed life of produced vehicles. Therefore, hydraulic servo actuators mounted on accelerated life testing equipment for automotive parts are essential for much higher performance and a longer life than those tested. However, small- and medium-sized companies that supply test equipment for the fatigue life of auto often fail to develop technology due to a lack of research personnel and the development budget compared to the capabilities of large automobile manufacturers, resulting in frequent breakdowns due to the technical overload of test equipment. In this study, servo actuators were used to test automotive parts, with a maximum output of 2 ton, a maximum frequency of 3.3 Hz and a maximum displacement of 50 mm. The hydraulic servo actuator, which was installed in the tensile compression fatigue life test equipment, failed to operate normally at the site, and by analyzing it, we realized this resulted from the heat generation of insulation compression due to the accumulation of air and gas into the hydraulic oil and the increase in friction due to the deterioration of flow. A static pressure bearing was adopted as a design change to improve the root cause for this failure mode, and a very high level of geometric concentricity was secured by inserting concentric tubes outside the labyrinth seal type piston. The newly designed and manufactured actuator is the result of research that has achieved a semi-permanent long life and improved performance up to 100 Hz by non-contact operation.

Fatigue Life Analysis and Tensile Overload Effects with High Strength Steel Notched Specimens

1983 ◽  
Vol 22 ◽  
Author(s):  
J. H. Underwood
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Cracking ◽  
High Strength ◽  
Pressure Vessels ◽  
Life Testing ◽  
Stress Concentrations ◽  
Notched Specimens ◽  
Life Analysis ◽  
Fatigue Life Analysis

Pressure vessels often have notches or other stress concentrations present. Considering further that pressure vessels are nearly always subjected to some cyclic loading, fatigue cracking at notches is an important problem. The objective here is to describe some fatigue life testing and analysis which was performed with notched specimens in order to determine the effects of notch overload on fatigue life of pressure vessels.

Sign in / Sign up

Export Citation Format

Share Document